This invention relates to a timing device and, more particularly, to a magneto-pneumatic timing device that may be used to provide a timed pressure signal for an end use and which has few moving parts and yet which has a output signal waveform that is easily modified in shape and in timing cycle.
Pneumatic timing devices are currently used for various purposes and are intended to provide a timed output pressure signal where that signal cycles between a higher and a lower value. The timing ratio between the signals, that is, the duty cycle as well as the overall time cycle may vary depending upon the particular application of or use for that signal. In any event, the timed output pressure signal can thus be used to control some end use device. An example of such an end use device is an intermittent suction device used in the withdrawal of fluid from a medical patient and is described in copending patent application by the same assignee as the present application and entitled "Magneto-Pneumatic Intermittent Suction Device", Ser. No. 995,391, filed Dec. 22, 1992 the disclosure of which is made part of the present application.
One of the features desired in such timing devices is that the device be reliable and be capable of functioning without supervision or maintenance for long periods of time and, accordingly, it is desired that the device have a minimum of moving parts that could wear out. The device should also be easy and inexpensive to manufacture. The latter feature requires that the components be relatively inexpensive and the assembly be simple and free of complex steps and extremely close tolerances.